The present invention relates to a sheet feeder which feeds sheets of paper stacked within a hopper one by one from the uppermost one to an apparatus such as a printer etc.
Some of the printers coupled to the personal computers are provided with sheet feeders. Such a sheet feeder supplies sheets of paper stacked on the hopper one by one from the uppermost one to a transferring roller of the printer by using a sheet feeding roller and a separation pad of a sheet feeding roller unit.
Then, the transfer operation of the transferring roller and the recording operation of a recording head are alternately executed with respect to the sheet thus supplied to the transferring roller of the printer, thereby to record an image including characters on the sheet thus transferred, and the sheet thus recorded is ejected.
A sheet returner and an idle roller are also provided at the sheet feeding roller unit. The sheet feeding roller unit operates after the rear end of the uppermost sheet moves away from a nipping portion between the separation pad and the idle roller to thereby return on the hopper the next-positioned sheet which leading end is located on the separation pad.
However, a plurality of, usually, two sheet feeding roller units each configured in the aforesaid manner are provided in a sheet feeding passage. It is sufficient, according to the present invention, to provide the single sheet feeding roller unit in the sheet-width direction in order to supply the sheet to the printer by using the sheet feeding roller and the separation pad of the sheet feeding roller unit. In view of such a fact, it is not ideal to provide a plurality of sheet feeding roller units in the width direction of the sheet feeding passage, and the provision of the plural sheet feeding roller units results in the increase of the number of the parts.
However, it is necessary to dispose the plural sheet feeding roller units provided with the sheet returners in the width direction of the sheet feeding passage in order to return the sheet which leading end is located on the separation pad on the hopper without being skewed by the sheet returners.
Further, the hopper of the sheet feeder is provided with an edge guide which is slidable in the width direction of the sheet. There is a sheet feeder which is configured in a manner that one of the sheet feeding roller units is coupled to the edge guide and slidable together with the edge guide in the width direction of the sheet. However, according to such a sheet feeder, the resistance (sliding load) caused at the time of sliding the edge guide becomes large and so the operability of the edge guide is degraded.
On the other hand, when the sheet is nipped between the sheet feeding roller in the sheet feeding roller unit and the separation pad, a force from the separation pad toward the sheet feeding roller, that is, a force directed to a back face of a separation pad holder for supporting the separation pad acts. The nipping state between the sheet feeding roller and the separation pad becomes insufficient due to the action of the force in the back face direction, so that there may occur such a phenomenon that the sheets are not supplied well one by one by the sheet feeding roller and the separation pad.
In view of the aforesaid circumstances, an object of the invention is to provide a sheet feeder which can return a sheet without being skewed, supply well a sheet to a sheet supply target from the hopper and realize the benefits. Further, another object of the invention is to provide a sheet feeder which can secure preferably the pressure contact state between a sheet feeding roller and a separation pad and supply a sheet well to the sheet supply target from the hopper.
In order to achieve the above objects, according to the present invention, there is provided a sheet feeder for feeding sheets of a recording medium to a recording apparatus comprising:
a hopper, on which the sheets of recording medium are stacked;
a sheet feeding roller, which is brought into contact with an uppermost sheet stacked on the hopper, and rotates to feed the uppermost sheet to the recording apparatus;
a separation pad, which presses the uppermost sheet against the feeding roller so that the upper most sheet is separated from a next uppermost sheet;
a first sheet returner, which pushes back a first part of the next uppermost sheet situated on the separation pad to the hopper; and
a second sheet returner, which pushes back a second part of the next uppermost sheet situated on the separation pad to the hopper,
wherein the sheet feeding roller, the separation pad and the first sheet returner are incorporated in a single unit which is disposed at a first position of a sheet feeding passage formed on the hopper, and the second sheet returner is solely disposed at a second position of the sheet feeding passage.
In this configuration, since the required number of parts are decreased, not only the sheet can be returned without being skewed and supplied well to the recording apparatus from the hopper, but also the benefits of the sheet feeder can be realized.
Preferably, the first sheet returner and the second sheet returner are provided immovably in a widthwise direction of the sheet feeding passage.
In this configuration, since none of the first sheet returner or the second sheet returner moves in the widthwise direction of the sheet feeding passage in cooperation with a slidable edge guide of the hopper, the resistance (sliding load) caused at the time of sliding the edge guide can be reduced and so the sliding operation of the edge guide can be performed smoothly.
Preferably, the sheet feeder further comprises guide members which are separately provided in the vicinity of the first sheet returner and the second sheet returner, each of the guide members having a guide face which forms a part of the sheet feeding passage.
In this configuration, as compared with the case where these guide members are formed continuously in the widthwise direction of the sheet feeding passage, even if the next uppermost sheet on the hopper which leading end is positioned at the separation pad is skewed or warped, the sheet is guided by the guide members by the operation of the first and second sheet returners and so the next uppermost sheet can be surely returned to the hopper. Therefore, in accordance with the forward rotation of the sheet feeding roller which is operated next, only the next uppermost sheet on the hopper can be supplied to the recording apparatus, and the sheets can be prevented from being supplied in a duplicated manner.
Preferably, the hopper includes an edge guide member, on which one side edges of the stacked sheets are aligned. Here, the first position of the sheet passage is in the vicinity of the edge guide member. A distance between the edge guide member and the second position almost corresponds to a width of a sheet having a size in a range from A6 to B5.
In this configuration, the sheet having the size equal to or smaller than almost A6 is returned to the hopper only by the first sheet returner, the sheet having the size in a range larger than almost A6 and to almost B5 is returned to the hopper only by the first sheet returner or by both the first and second sheet returners, and the sheet having the size larger than almost B5 is returned to the hopper by both the first and second sheet returners. In this manner, any sizes of the sheet can be surely returned to the hopper by these sheet returners without being skewed.
Preferably, the second sheet returner includes a sheet returning lever, and a lever cam, which is integrally provided with a rotary shaft of the sheet feeding roller, for operating the sheet returning lever.
In this configuration, the accuracy of the parts of the lever cam can be improved and the number of the parts thereof can be reduced.
According to the present invention, there is also provided a sheet feeder for feeding sheets of a recording medium to a recording apparatus, comprising:
a hopper, on which the sheets of recording medium are stacked;
a sheet feeding roller, which is brought into contact with an uppermost sheet stacked on the hopper, and rotates to feed the uppermost sheet to the recording apparatus;
a separation pad, which presses the uppermost sheet against the feeding roller so that the upper most sheet is separated from a next uppermost sheet; and
a cover member, which covers the sheet feeding roller, and is secured to the recording apparatus such that a force acting from the separation pad to the sheet feeding roller when the uppermost sheet is fed is received by the recording apparatus.
Here, it is preferable that the cover member is formed with a hook member engaged with a part of the recording apparatus so that the force is received by the recording apparatus through the hook member.
In this configuration, the sheet feeding roller is prevented from moving to a direction to which the force is acted when the sheet is fed to the recording apparatus. As a result, the pressure contacting state between the sheet feeding roller and the separation pad is secured well and the sheet can be supplied well to the recording apparatus from the hopper.